在iOS中实现Porter-Duff合成操作

Question

iOS SDK中是否有Porter-Duff合成操作？

基础12 Porter-Duff合成操作。

Answer 1

iOS CoreGraphics框架支持以下类型的混合模式，包括Porter-Duff。

typedef CF_ENUM (int32_t, CGBlendMode) {
    /* Available in Mac OS X 10.4 & later. */
    kCGBlendModeNormal,
    kCGBlendModeMultiply,
    kCGBlendModeScreen,
    kCGBlendModeOverlay,
    kCGBlendModeDarken,
    kCGBlendModeLighten,
    kCGBlendModeColorDodge,
    kCGBlendModeColorBurn,
    kCGBlendModeSoftLight,
    kCGBlendModeHardLight,
    kCGBlendModeDifference,
    kCGBlendModeExclusion,
    kCGBlendModeHue,
    kCGBlendModeSaturation,
    kCGBlendModeColor,
    kCGBlendModeLuminosity,

    /* Available in Mac OS X 10.5 & later. R, S, and D are, respectively,
       premultiplied result, source, and destination colors with alpha; Ra,
       Sa, and Da are the alpha components of these colors.

       The Porter-Duff "source over" mode is called `kCGBlendModeNormal':
         R = S + D*(1 - Sa)

       Note that the Porter-Duff "XOR" mode is only titularly related to the
       classical bitmap XOR operation (which is unsupported by
       CoreGraphics). */

    kCGBlendModeClear,                  /* R = 0 */
    kCGBlendModeCopy,                   /* R = S */
    kCGBlendModeSourceIn,               /* R = S*Da */
    kCGBlendModeSourceOut,              /* R = S*(1 - Da) */
    kCGBlendModeSourceAtop,             /* R = S*Da + D*(1 - Sa) */
    kCGBlendModeDestinationOver,        /* R = S*(1 - Da) + D */
    kCGBlendModeDestinationIn,          /* R = D*Sa */
    kCGBlendModeDestinationOut,         /* R = D*(1 - Sa) */
    kCGBlendModeDestinationAtop,        /* R = S*(1 - Da) + D*Sa */
    kCGBlendModeXOR,                    /* R = S*(1 - Da) + D*(1 - Sa) */
    kCGBlendModePlusDarker,             /* R = MAX(0, (1 - D) + (1 - S)) */
    kCGBlendModePlusLighter             /* R = MIN(1, S + D) */
};

以下Apple开发人员链接，演示了如何实现Porter-Duff混合。

https://developer.apple.com/library/ios/samplecode/QuartzDemo/Listings/QuartzDemo_QuartzBlendingViewController_m.html

希望这有帮助。